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Thanks for posting.

It's not the same rolling diameter as the regular tires. Somewhere deep in some BMW tech' training literature there was a blurb that when the xDrive logic detects a spare tire installed it disengages the front wheel drive. Most punctures happen on the back. If you have a square set-up, it's probably a good idea to put a good tire on the back and the spare on the front. Those mismatched rolling diameters on the rear could play havoc with a limited slip differential.

So far, Frau Putzer's X3's spare has only been installed as a place holder during my DIY tire rotations.
 

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Your link sort of proved my point. The went 250 miles with no problems. There's no specific mileage limit on donuts. There is a speed limit. My plan for limping home on a donut is to put it on the front axle. I carry a hand pump with me on road trips, so the donut would be properly inflated if I used it.

I'm not trusting my car, wheel, and tire to the first jackass tire ape I come to after getting a flat tire. I'll limp home and take the flat tire to a competent shop, e.g. BMWoB. (BMWoB did my tire work for my Chevy Cobalt SS, because I don't trust anybody in Bubba County.)
 

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I think that's the exception rather than the rule, I think if you can't find a BMW dealer or reputable tire shop in 250 miles, there's a serious problem.

It's not a full size spare, end of, it's a get you home or get you to a garage fix.

Anyway, I don't wanna keep beating this argument to death, so I'll bow out
Welcome to Floriduh!

"Reputable" means they have a $50k lever-less tire machine that doesn't scratch up my wheels. The new Discount Tires store in Bubbaville has four tire machines, all the $10k POS lever machines that scratch wheels. "We won't scratch your wheels. We'll be real careful. ... promise." "Shazam! How'd that wheel get scratched?"

No thanks!
 

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Couldn't you have ordered a space saver spare from BMW for $150 when you ordered your car? Maybe they didn't give you this option when you ordered 20" tires.:unsure:
The 20" wheel diameter isn't the problem. The Tire & Cooling Package has bigger brakes. The 18" spare (common on all G20's) can't fit over the big brakes in the front. That's also why you can't get a spare on the X2 M35i.

The weak links on fast BMW's under track use are tires, brakes, and engine overheating. I'd want the Tire & Cooling Package on an M340i.
 
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